1. Field of the Invention
The present invention relates to a relay server that enables communication to be performed between apparatuses connected to different LANs (Local Area Networks).
2. Description of the Related Art
Conventionally, a communication technology called a virtual private network (Virtual Private Network, VPN) has been known, which allows communication to be performed between LANs installed in physically distant places. Japanese Patent Application Laid-Open No. 2010-268312 shows an example in which a relay server, a communication terminal, and the like, are connected to each of a plurality of LANs installed in physically distant places. With the use of the VPN, a communication terminal is able to transmit a packet to a communication terminal connected to another LAN. More specifically, a packet transmitted by a communication terminal is firstly sent to a relay server belonging to a LAN that the communication terminal belongs to. This relay server transmits (forwards) the packet, via Internet, to a relay server belonging to a LAN that a destination communication terminal belongs to. The relay server receives the packet, and transmits (forwards) the packet to the destination communication terminal.
Use of the VPN enables another LAN located in a distant place to be used as if it is a directly-connected network.
In this type of system, communication between terminals is performed with the use of IP addresses (private IP addresses) of terminals that are connected to LANs. The IP addresses are assigned without any overlap in the same LAN, but may overlap among terminals that are connected to different LANs. In such a case, two or more identical IP addresses exist in the VPN, which makes it impossible to perform proper communication.
To avoid such a situation, conventionally, when there are overlapping IP addresses, the VPN is once terminated and then re-setting of IP addresses is performed. This puts a burden on a user, because the user has to perform the setting by hand each time overlapping IP addresses are detected.